The major objective of this grant is to determine the levels of antibodies in saliva and serum from caries-defined and periodontal disease-defined subjects to immunoglobulin A1 (IgA1) and IgG proteases isolated from culture supernatants of Streptococcus sanguis and Capnocytophaga ochracea, respectively. Naturally occurring antibodies to IgA1 protease in saliva and serum have recently been reported; however, it is not known if there are differences in the levels of these antibodies between various groups of individuals. IgA1 protease cleaves a particular proline/threonine linkage in the hinge region of the IgA1 subclass of IgA rendering it nonfunctional and it therefore is an important virulence factor which is produced by several different mucosal pathogens. IgG protease also cleaves the immunoglobulin which abrogates its' functional activity, however, much less is known about this enzyme than IgA1 protease. The purity and activity of the IgA1 and IgG protease antigens to be used to establish antibody levels will be determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunosorbent assay (ELISA). Salivary and serum antibody levels will be determined using SDS-PAGE and ELISA and homogenous preparations of S. sanguis IgA1 and Capnocytophaga IgG proteases. Caries-resistant and -susceptible and periodontal disease-resistant and -susceptible individuals will be recruited using strict criteria. It is anticipated that caries-resistant and periodontal disease-resistant subjects will have higher levels of salivary and serum antibodies, respectively, to IgA1 and IgG proteases than caries-susceptible and periodontal disease-susceptible subjects. The higher levels of antibodies to IgA1 and IgG proteases in resistant individuals may prevent the enzymes from cleaving IgA1 and IgG, whereas the lower antibody levels in susceptible subjects may not neutralize the enzymes sufficiently to prevent them from cleaving IgA1 and IgG. The IgA1 and IgG proteases in the oral cavities of susceptible individuals may then cleave more potentially protective IgA and IgG antibodies and thus these subjects may be more at risk from disease than those having higher levels of enzyme-neutralizing antibodies. These proposed studies will significantly advance our understanding of the action of AgA1 and IgG proteases and their immunological properties.